1. Field of the Invention
The present invention relates to an electrostatic charger and an electrostatic discharger, which can be respectively applied to a charging unit and a charge removing unit in an image forming apparatus such as a copying machine, a facsimile apparatus, a printer, or the like, which uses an electrophotography technique.
2. Related Background Art
An image forming process in a copying machine, a facsimile apparatus, a printer, or the like, which uses an electrophotography technique, includes a charging process for electrostatically charging the major surface (the surface to be charged) of a photoreceptor or photoconductor as a member to be charged. Conventionally, the charging process is attained by a corona charger, which can attain this process in a non-contact manner and has excellent charging stability. However, since this system produces a large amount of ozone, a contact charging system has been examined recently. For example, a contact charging method (a roller charging system using a conductive roller; an AC voltage is superposed on a DC voltage, and the obtained voltage is applied to the conductive roller) disclosed in Japanese Patent Laid-Open No. 63-149669, a brush charging apparatus (a brush charging system using a conductive brush; a low-resistance intermediate conductive member is arranged between the conductive brush and the core metal, and the surface of the member to be charged is uniformly charged while removing environmental dependence of charging) disclosed in Japanese Patent Laid-Open No. 6-175469, and the like, have been put into practical applications.
Furthermore, the above-mentioned image forming process in a copying machine, a facsimile apparatus, a printer, or the like, which uses the electrophotography technique, also includes a charge removing process for removing charges from a photoconductor, a recording paper sheet, and the like. As a charge removing method for a photoconductor, techniques for removing a charge using short-wavelength light are disclosed in, e.g., Japanese Patent Laid-Open Nos. 62-38491, 1-274186, and 2-256084. These charge removing methods relate to charge removal for an organic photoconductor (OPC). With these methods, by irradiating short-wavelength light from a charge removal lamp onto a photoconductor to remove a charge therefrom, a charge trapped deep inside a photoconductive layer can be released without deteriorating the charging performance of the photoconductor.
As a charge removing method and apparatus for a charged object, although they do not relate to charge removal of a photoconductor, for example, Japanese Patent Laid-Open No. 7-161485 discloses a technique for removing the charge on the charged object by irradiating ultraviolet rays from an ultraviolet ray irradiation device onto the charged object to ionize a gas in the atmosphere in which the charged object is placed or to release excessive ions staying inside the charged object.